An auxiliary air conditioning, heating and engine warming system for trucks is disclosed in my U.S. Pat. No. 4,682,649 dated Jul. 28, 1987, the disclosure of which is incorporated herein by reference.
Basically, main and auxiliary vehicle air conditioning systems operate in such a way that when the truck is running, as when the truck is traveling or stopped for a short time period only, the truck air conditioning and heating systems operate in a conventional manner to supply conditioned air or warm air to the truck cab and/or sleeping compartment. At this time, the auxiliary power plant is inactive and has no effect on the operation of the truck air conditioning and heating systems or its electrical system.
When the truck stops for a lengthy period and its engine is turned off, the auxiliary air conditioning system is activated to not only supply conditioned air to the truck cab and/or sleeping compartment but also for warming the truck engine and its fuel lines.
In the system disclosed in my aforementioned patent, a pair of cut-off valves were provided in the refrigerant pressure lines for isolating the main air conditioning system from the auxiliary air conditioning system or for isolating the auxiliary air conditioning system from the main conditioning system.
After considerable research and experimentation, the isolation valve of the present invention has been devised for replacing the pair of cut-off valves disclosed in my aforementioned patent.